Localized structures and spatial correlations in lasers with multiphoton emission

Summary form only given. The present communication investigates the transverse dynamics of broad-area three-level cascade lasers, for which one and two-photon emission processes coexist under general conditions. When the two emitted electromagnetic fields have widely different intensities, the transverse spectrum of the weakest beam reveals the underlying AC-Stark splitting induced by the most intense one. Under these conditions, spatial correlations between the two emitted transverse patterns can be clearly observed, in what provides the first example of such phenomenology in active optical media. In the parameter regime where both one and two-photon emission are comparably important, the correlation far-field profile reflects this coexistence by displaying minima for wave vectors corresponding to the former emission processes and maxima for the latter ones. Under more general conditions, however, the system exhibits complex, nonstationary spatio-temporal dynamics. Among all different types of behavior displayed by the system in this situation, we can point out the appearance of localized structures, encompassing both intensity maxima (cavity solitons) and minima (optical vortices). In particular, in effective two-photon resonance, solitons emerge spontaneously as a globally attracting state of the system dynamics. This fact contrasts with the locally attracting character of cavity solitons found previously in passive media and in lasers with intracavity absorbing elements. For large enough pump rates, the system develops a turbulent state in which a large number of solitons interact in a complex way.